Answer: an ice age
Explanation:
An ice age refers to a period of prolonged continental glaciation. An ice age refers to a period when the temperature of the Earth's climate is very low for a long period of time.
This then brings about an expansion of the polar ice sheets, mountain glaciers and the continental ice sheets. Ice age, can also be referred to as the glacial age, and it's a period when there are thick ice sheets that cover areas of land.
